veriexec: Additional functionality for MAC/veriexec

Ensure veriexec opens the file before doing any read operations.

When the MAC_VERIEXEC_CHECK_PATH_SYSCALL syscall is requested, veriexec
needs to open the file before calling mac_veriexec_check_vp. This is to
ensure any set up is done by the file system. Most file systems do not
explicitly need an open, but some (e.g. virtfs) require initialization
of access tokens (file identifiers, etc.) before doing any read or write
operations.

The evaluate_fingerprint() function needs to ensure it has an open file
for reading in order to evaluate the fingerprint. The ideal solution is
to have a hook after the VOP_OPEN call in vn_open. For now, we open the
file for reading, envaluate the fingerprint, and close the file. While
this leaves a potential hole that could possibly be taken advantage of
by a dedicated aversary, this code path is not typically visited often
in our use cases, as we primarily encounter verified mounts and not
individual files. This should be considered a temporary workaround until
discussions about the post-open hook have concluded and the hook becomes
available.

Add MAC_VERIEXEC_GET_PARAMS_PATH_SYSCALL and
MAC_VERIEXEC_GET_PARAMS_PID_SYSCALL to mac_veriexec_syscall so we can
fetch and check label contents in an unconstrained manner.

Add a check for PRIV_VERIEXEC_CONTROL to do ioctl on /dev/veriexec

Make it clear that trusted process cannot be debugged. Attempts to debug
a trusted process already fail, but the failure path is very obscure.
Add an explicit check for VERIEXEC_TRUSTED in
mac_veriexec_proc_check_debug.

We need mac_veriexec_priv_check to not block PRIV_KMEM_WRITE if
mac_priv_gant() says it is ok.

Reviewed by:	sjg
Obtained from:	Juniper Networks, Inc.

3 files changed, 195 insertions, 1 deletions

diff --git a/lib/libveriexec/Makefile b/lib/libveriexec/Makefile
index 2c68faf3356f..84e2b8329967 100644
--- a/lib/libveriexec/Makefile
+++ b/lib/libveriexec/Makefile
@@ -8,7 +8,9 @@ INCS=		libveriexec.h
 
 WARNS?=		2
 
-SRCS=		veriexec_check.c
+SRCS= \
+	veriexec_check.c \
+	veriexec_get.c
 
 .include <bsd.lib.mk>
 
diff --git a/lib/libveriexec/libveriexec.h b/lib/libveriexec/libveriexec.h
index 42d2c964a174..d186db0ab8d9 100644
--- a/lib/libveriexec/libveriexec.h
+++ b/lib/libveriexec/libveriexec.h
@@ -29,9 +29,17 @@
 #ifndef __LIBVERIEXEC_H__
 #define __LIBVERIEXEC_H__
 
+struct mac_veriexec_syscall_params;
+
 int	veriexec_check_fd_mode(int, unsigned int);
 int	veriexec_check_path_mode(const char *, unsigned int);
 int	veriexec_check_fd(int);
 int	veriexec_check_path(const char *);
+int	veriexec_get_pid_params(pid_t, struct mac_veriexec_syscall_params *);
+int	veriexec_get_path_params(const char *,
+	    struct mac_veriexec_syscall_params *);
+int	veriexec_check_pid_label(pid_t, const char *);
+
+#define	HAVE_VERIEXEC_CHECK_PID_LABEL	1
 
 #endif  /* __LIBVERIEXEC_H__ */
diff --git a/lib/libveriexec/veriexec_get.c b/lib/libveriexec/veriexec_get.c
new file mode 100644
index 000000000000..46df6eecf76e
--- /dev/null
+++ b/lib/libveriexec/veriexec_get.c
@@ -0,0 +1,184 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2021-2023, Juniper Networks, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+#include <sys/types.h>
+#include <sys/errno.h>
+#include <sys/mac.h>
+
+#include <unistd.h>
+#include <string.h>
+
+#include <security/mac_veriexec/mac_veriexec.h>
+
+/**
+ * @brief get veriexec params for a process
+ *
+ * @return
+ * @li 0 if successful
+ */
+int
+veriexec_get_pid_params(pid_t pid,
+    struct mac_veriexec_syscall_params *params)
+{
+	struct mac_veriexec_syscall_params_args args;
+
+	if (params == NULL)
+		return EINVAL;
+
+	args.u.pid = pid;
+	args.params = params;
+	return mac_syscall(MAC_VERIEXEC_NAME,
+	    MAC_VERIEXEC_GET_PARAMS_PID_SYSCALL, &args);
+}
+
+/**
+ * @brief get veriexec params for a process
+ *
+ * @return
+ * @li 0 if successful
+ */
+int
+veriexec_get_path_params(const char *file,
+    struct mac_veriexec_syscall_params *params)
+{
+	struct mac_veriexec_syscall_params_args args;
+
+	if (file == NULL || params == NULL)
+		return EINVAL;
+
+	args.u.filename = file;
+	args.params = params;
+	return mac_syscall(MAC_VERIEXEC_NAME,
+	    MAC_VERIEXEC_GET_PARAMS_PATH_SYSCALL, &args);
+}
+
+/**
+ * @brief check if label contains what we want
+ *
+ * @return
+ * @li 0 if no
+ * @li 1 if yes
+ */
+int
+veriexec_check_pid_label(pid_t pid, const char *want)
+{
+	struct mac_veriexec_syscall_params params;
+	char *cp;
+	size_t n;
+
+	if (want != NULL &&
+	    veriexec_get_pid_params(pid, &params) == 0) {
+		/* Does label contain [,]<want>[,] ? */
+		if (params.labellen > 0 &&
+		    (cp = strstr(params.label, want)) != NULL) {
+			if (cp == params.label || cp[-1] == ',') {
+				n = strlen(want);
+				if (cp[n] == '\0' || cp[n] == ',')
+					return 1; /* yes */
+			}
+		}
+	}
+	return 0;			/* no */
+}
+
+#ifdef UNIT_TEST
+#include <stdlib.h>
+#include <stdio.h>
+#include <err.h>
+
+static char *
+hash2hex(char *type, unsigned char *digest)
+{
+	static char buf[2*MAXFINGERPRINTLEN+1];
+	size_t n;
+	int i;
+
+	if (strcmp(type, "SHA1") == 0) {
+		n = 20;
+	} else if (strcmp(type, "SHA256") == 0) {
+		n = 32;
+	} else if (strcmp(type, "SHA384") == 0) {
+		n = 48;
+	}
+	for (i = 0; i < n; i++) {
+		sprintf(&buf[2*i], "%02x", (unsigned)digest[i]);
+	}
+	return buf;
+}
+
+int
+main(int argc, char *argv[])
+{
+	struct mac_veriexec_syscall_params params;
+	pid_t pid;
+	char *want = NULL;
+	int pflag = 0;
+	int error;
+	int c;
+
+	while ((c = getopt(argc, argv, "pw:")) != -1) {
+		switch (c) {
+		case 'p':
+			pflag = 1;
+			break;
+		case 'w':
+			want = optarg;
+			break;
+		default:
+			break;
+		}
+	}
+	for (; optind < argc; optind++) {
+
+		if (pflag) {
+			pid = atoi(argv[optind]);
+			if (want) {
+				error = veriexec_check_pid_label(pid, want);
+				printf("pid=%d want='%s': %d\n",
+				    pid, want, error);
+				continue;
+			}
+			error = veriexec_get_pid_params(pid, &params);
+		} else {
+			error = veriexec_get_path_params(argv[optind], &params);
+		}
+		if (error) {
+			err(2, "%s, error=%d", argv[optind], error);
+		}
+
+		printf("arg=%s, type=%s, flags=%u, label='%s', fingerprint='%s'\n",
+		    argv[optind], params.fp_type, (unsigned)params.flags,
+		    params.label,
+		    hash2hex(params.fp_type, params.fingerprint));
+	}
+	return 0;
+}
+#endif